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Published byClaire Russell Modified over 9 years ago
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The final saga
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There is an activation energy for each elementary step. Activation energy determines k. k = Ae - (E a /RT) k determines rate Slowest step (rate determining) must have the highest activation energy.
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This reaction takes place in three steps
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EaEa First step is fast Low activation energy
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Second step is slow High activation energy EaEa
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EaEa Third step is fast Low activation energy
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Second step is rate determining
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Intermediates are present
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Activated Complexes or Transition States
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Speed up a reaction without being used up in the reaction. Enzymes are biological catalysts. Homogenous Catalysts are in the same phase as the reactants. Heterogeneous Catalysts are in a different phase as the reactants.
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Catalysts allow reactions to proceed by a different mechanism - a new pathway. New pathway has a lower activation energy. More molecules will have this activation energy. Does not change E Show up as a reactant in one step and a product in a later step
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Pt surface HHHH HHHH Hydrogen bonds to surface of metal. Break H-H bonds
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Pt surface HHHH C HH C HH
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HHHH The double bond breaks and bonds to the catalyst. C HH C HH
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Pt surface HHHH The hydrogen atoms bond with the carbon C HH C HH
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Pt surface H C HH C HH HHH
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Chlorofluorocarbons (CFCs) catalyze the decomposition of ozone. Enzymes regulating the body processes. (Protein catalysts)
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Catalysts will speed up a reaction but only to a certain point. Past a certain point adding more reactants won’t change the rate. Zero Order
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Rate increases until the active sites of catalyst are filled. Then rate is independent of concentration Concentration of reactants RateRate
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